Improved textile yarn windup mechanism



Nov. 21, 1961 R. AKERS IMPROVED TEXTILE YARN WINDUP MECHANISM Filed June 24, 1960 3 Sheets-Sheet 1 FIG-I R INVENTOR RICHARD LAWRENCE AKERS ATTORNEY Nov. 21, 1961 R. L. AKERS 3,0 9,

IMPROVED TEXTILE YARN WINDUP MECHANISM Filed June 24, 1960 3 Sheets-Sheet 2 FIG. 3

INVENTOR memo LAWRENCE AKERS BY 2 6 W ATTORNEY Nov. 21, 1961 R.-L. AKERS IMPROVED TEXTILE YARN WINDUP MECHANISM 3 Sheets-Sheet 3 Filed June 24, 1960 A N N United States Patent 3,009,661 IMPRGVED TEXTILE YARN WINDUP MECHANISM Richard Lawrence Alters, Ciayrnont, Deh, assignor to E. I. du Pont de Nemonrs and Company, Wilmington,

Del., a corporation of Delaware Fiied June 24, 1960, cr. No. 38,557 3 Claims. (Cl. 242-13) This invention relates to winding of filamentous material such as threads, yarns, strands, and the like and particularly it relates to the high speed cross winding of synthetic textile fibers. It especially relates to an improved process and equipment for winding by means of a surface drive roll.

Windups employing a surface or friction drive are common in the art. It is well known in that art that proper textile yarn package formation is controlled in part by the length of yarn between the point at which it leaves the traverse mechanism guide and the point at which it lays down upon the bobbin or winding package. Known as the uncontrolled yarn length, this distance must be kept short, "for the longer it is, the greater the probability that overthrown ends, irregular package edges, and improperly formed surfaces will result. If the length is excessive, the package may lack stability and, furthermore may undergo considerable buildup at the ends where reversals occur causing the driven surface of the Package to have a saddle shaped appearance. Packages such as this do not handle properly in subsequent textile processing and when rotated by a drive roll subject the built-up portions to undue pressure and wear which damages the yarn. It is apparent that the uncontrolled yarn length may be kept constant by constraining the center of the growing package so that a straight line path is followed or approximated. However, as the package grows in size its periphery may interfere with the traverse guide if the initial uncontrolled yarn length was kept small and the traverse as a result was placed close to the winding package. Thus, most practical arrangements involving short uncontrolled yarn lengths have a length suited only to the final package diameter, the tip of the traverse guide being located at a point such that the final surface of the package approaches the tip of the guide closely but does not touch. At elevated operating speed, it has been observed that such excessive uncontrolled yarn length during initial stages of yarn windup on a given package makes yarn lay down improperly as previously described.

Synthetic filamentous materials are strain sensitive. It is important in handling these to keep strains uniform during processing so that the properties in the final package do not vary discernibly in a commercially undesirable manner. It is often the case that the angle at which yarn enters and passes across a traversing guide is variable and is greater than desired initially changing towards a smaller and more desirable angle as the package grows. It is also a requirement, however, that despite the growth of the package, the yarn line must always be contained within the traverse guide and not pulled away from the guiding surface. It is important, therefore, in any high speed process for strain sensitive material that the break angle or angle of bend of the yarn across the traverse guide be kept as small and as nearly constant as is consistent with other requirements of the packaging process and that the uncontrolled yarn length be kept small and substantially minimum. It is also essential that vibrating deviations in the position of the axis of the rotating package be eliminated to prevent uneven strains from developing as the yarn is being wound up.

It is seen, therefore, that in a practical operating system employing the concept of minimum uncontrolled yarn length throughout the winding process that the limiice tation is the possible spacing between the tip of the traverse guide and the surface or periphery of the package. It is this clearance that must be kept substantially constant despite the continuing increase in the diameter of the winding package. Assuming a given diameter bobbin, large diameter traversing cam and drive roll with respect to the package size, and fixed axes of rotation for the cam and drive roll, a mathematical expression for locating the path of the center of the winding package under these conditions may be obtained taking the root of the traverse guide as the origin. This expression is Y is equal to the square root of the quantity C +2XC where Y equals the uncontrolled yarn length, C equals the minimum allowable distance between the traverse point and the package surface, and X equals the radius of the package. This ideal path so defined, therefore, is not arcuate but is curved. With C being held constant, it will be recognized from this expression that the uncontrolled yarn length increases during the growth of the winding package. It follows as a result that any system of winding according to the formula will produce a package having slightly tapered end faces, the taper being inwards granting additional stability to the package. It must be recognized, however, that excessive length at any time would produce improper formation as described previously and, therefore, the uncontrolled yarn length must be chosen suitably short at all times to prohibit this occurrence.

The object of the invention is to provide an improved arrangement of methods and apparatus for the high speed cross winding of filamentous materials so that satisfactory yarn quality and package quality is maintained. A further Object is to maintain a minimum uncontrolled yarn length at all times during a given package formation. Still another object is to minimize the yarn break angle across the traverse guide and to hold the variation in this angle during winding to a minimum. Another object is to minimize or substantially eliminate vibrations or deviations of the package axis during winding while attaining the above objects. Other objectives and advantages of the invention will be apparent from the drawings and description hereinafter.

The difiiculties of the prior art have been overcome and the objects met by an improved winding arrangement in which the axis of the growing yarn package or cake is smoothly positively moved in spaced relation to a traverse mechanism fixed to the machine frame, the spaced relationship being so established that a substantially minimum uncontrolled yarn length is approximated at all stages of package growth, the approximation being such as to permit contact of the periphery of the growing cake with the driving surface of a fixed drive roll. In the preferred embodiment, this control of the spaced relationship is accomplished by suitably mounting the axis of the package holding mechanism on one of the links of a positively controlled four-bar linkage.

The following specification and claims are to be considered with the accompanying drawings in which:

FIGURE 1 is a schematic view or geometrical presentation illustrating the ideal path of the center of the winding package to maintain the relationship of constant clearance and minimum uncontrolled length previously described as Well as the path showing the approximation of this invention permitting the periphery of the winding package to be always in contact with a fixed center drive roll.

FIGURE 2 is a side elevational schematic view of a preferred embodiment of the invention.

FIGURE 3 is a front elevation of a windup machine embodying features of my invention in preferred form.

FIGURE 4 is a side view of the machine of FIGURE Referring to FIGURE 1 of the drawings, reference numeral 10 pertains to a vertical yarn line passing from processing equipment to be wound in a cross wound pack age and is shown traversed by reciprocating guide it operated by a traverse mechanism generally indicated by 12 ordinarily consisting of a cam and cover. It will be seen that displacement of yarn line It} in the direction to the left as shown on the drawing will withdraw the threadline from traverse guide 11 and so the vertical posi tion represents a limiting position in operation of the winding system. As previously described, it is desirable to maintain a close and fixed distance between the root of traverse guide 11 and the surface or periphery of the winding package and the locus of points at this distance are indicated by the dashed circle 13. If R represents the radius of the minimum package to be wound or, in other words, the radius of the bare bobbin or core employed, then it represents the ideal location for the axis of the cake in its initial position such that Y in the formula described previously is held to a minimum. Stated differently, u is the intersection of an are drawn from the root of traverse guide 11 having a radius equal to R plus the radius of circle 13 and a line parallel to yarn 10 at a distance from line 10 equal to R Similarly, if R represents the radius of the largest package which it is desired to wind, the 11' represents the center of that package according to the formula. The path uu' then is the ideal path as defined. If 14 represents a drive roll mounted rotatably about center 15 and having radius R the periphery of the largest diameter package, the one having the radius R must be tangent with the periphery of drive roll 14. The drive roll then may be located any place on the surface of the largest diameter package and is shown so located as close as is practical to traverse mechanism 12. The use of a fixed center drive roll 14 then eliminates the possibility that the center of the winding cake can follow path ll-ll' for it introduces the further requirement that each package diameter must always be tangent to the periphery of drive roll 14 as well as the other requirements previously stated. Thus, at any given stage of package growth, say at radius R the locus representing the concurrence of an are having a radius R plus R swung from center 15 and an arc having a radius of R plus the radius of circle 13 swung about the root of traverse guide 11 will be at point Point 0 represents such a point for the minimum diameter package and 00'-u' then represents the approximation to ideal path u--u such that the growing package is always in contact with the periphery of fixed center drive roll 14. It will be seen that Y, the minimum uncontrolled yarn length is the same for the two paths, i.e., path uu' and path 00'-u'. The triangle, formed by the root of the traverse guide 11, the center of the package, and the point of tangency of the yarn with the package, is rotated, unchanged, around the root of the traverse guide until the package contacts the drive roll; i.e., point It is rotated to become point 0. This rotation causes the incoming yarn to have a break angle and the magnitude of this angle is the same as the amount that the triangle was rotated.

Referring to the FIGURES 2, 3, and 4 reference numerals 10, 11, 12, 14, and 15 refer, as in FIGURE 1, to yarn line, traverse guide, traverse cam, drive roll and drive roll center respectively. Traverse cam housing 16 is shown surrounding traverse cam 12 and contains guide tracks for reciprocating guide 11; these tracks being conventional and well known are not shown. Bobbin 17 is shown mounted on bobbin support or chuck 18 at point 19 of swing arm 20. Swing arm 29 comprises one link of a four-bar linkage, the other three links being crank 21, rocker arm 22, and frame 23, which, as schematically indicated, in FIG. 2 is fixed. This fourbar linkage not only supports the bobbin but 'by virtue of the restraint offered by the links fully and in a positive manner defines the path through which the center of bobbin 17 moves. This path is neither arcuate nor straight line but 4 generally takes the form of a distored ellipse and is shown as dashed line 24.

A tension spring 25 is secured to rocker arm 22 and swing arm 20 in such a way that the tensile force exerted by spring 25 tends to decrease the angle X between swing arm 20 and rocker arm 22. Crank 21 is extended beyond both of its two pivot points 26 and 27. The bottom extension of crank 21 strikes the arm of hydraulic dash pot 28 when the swing arm 20 is manually pulled out and has nearly reached the dotting position in path 24. This dash pot cushions the descending masses. The upper extension of crank 21 carries an integral counter weighting mass or counter-weight 30. Suitable stops, not shown, on the linkages 20, 21, 22 and 23 prevent the four-bar linkage from being swung to the extremes where the center of bobbin 17 would follow path 24 around the return loop at either end of the distorted ellipse which the four-bar linkage defines as the path.

To obtain good quality packages, it is necessary to maintain substantially constant pressure between the package and the drive roll 14 throughout the growth of the package. This is accomplished in this windup by the mechanisms described below. The package to drive roll pressure is a function of the interaction of the weight of links 20, 21, 22, and counterweight 30, the force of spring 25, and the growing weight of the package. When the package is small, the weights alone are not sutficient to create the proper pressure of the package against the drive roll. The desired pressure is obtained by the additional force from spring 25.

As the package grows in size, the increasing weight at first tends to decrease the pressure. Gradually this effect lessens and finally the increasing weight tends to increase the pressure. During the early stages of package growth the angle X between swing arm 20 and rocker arm 22 is increasing at a non-linear rate. This causes an increase in the force from spring 25 which counteracts the etfect of the increased package weight.

At the same time, however, counterweight 30 on crank 21 contributes a counterclockwise torque on crank 21 because its center of gravity 31 is located to the left of vertical centerline WW. The torque is a sinusoidal function of the angle that the center of gravity 31 is displaced away from ccnterline WW. When the bobbin has no yarn on it, center of gravity 31 of counterweight 30 is close to vertical centerline WW; hence, the torque effect of the counterweight 30 is negligible. As the package begins to grow and increase in weight, the distance of the center of gravity 31 of counterweight 30 from vertical center line WW increases rapidly, and the increasing torque elfect acts to counteract the increase in pressure which would result both from the increased extension of spring 25 and increased package weight. At a certain stage in the growth of the package, the angle X between rocker arm 22 and swing arm 30 ceases to increase to a significant extent, so that from this point on the spring 25 does not increase its tendency to add to the pressure. During the final stages of package growth, the increase in torque effect from the counterweight is thus fully utilized in counteracting the additional weight of the package. The end result of the interaction just described is to maintain a substantially constant pressure between the package and drive roll throughout the growth of the package.

When the swing arm 20 is manually displaced from full package position 32 to a doff position, angle X decreases, relaxing the spring 25, so that it oifers no resistance to the operator. A preferred embodiment of structure embodying these inventive features is shown in FIGS. 3 and 4. This represents a considerable advantage over conventional methods of counterbalancing the weight of a growing package.

The linkage previously described has the advantage that the clearance between the periphery of the package and the tip of the yarn traverse guide is substantially constant at all times. Furthermore, the uncontrolled yarn length is kept small. The uncontrolled yarn length, which is kept close to the minimum, changes in the preferred direction of becoming slightly longer as the package grows larger, thus causing the package to taper slightly inward adding to its stability. For a given cam drive roll and bobbin diameter and an arbitrary maximum yarn break angle this windup will produce a larger package than that of a conventional swing arm windup. The linkage disclosed has a further advantage in that it maintains constant positive control over movement of the package axis and swing arm 20 by reason of the direct linking of arm 22 and crank 21 to swing arm 20. This complete control helps eliminate erratic motion or vibration of the package while rotating at high speeds and consequent strains in the yarn.

The four-bar linkage shown and described herein need not necessarily have the dimensions and proportions indicated because other four-bar links configurations will provide the required bobbin path for obtaining short uncontrolled yarn lengths, w yarn break angle, and follow the path approximating the ideal and permitting drive roll contact as described previously. In addition, all the description heretofore has been directed to a yarn traverse guide which is driven by a cam roll. This invention can equally be applied to other types of yarn guiding mechanisms such as a traverse roll.

It is to be understood that the invention is not to be limited except as set forth in the claims.

I claim:

1. An improved yarn windup apparatus comprising a supporting frame structure, a windup chuck, means rotatably mounting said chuck in said frame structure, a yarn windup bobbin mounted on said chuck, a driven roll mounted on said frame structure and engaged with said windup bobbin to rotate the same, a yarn traversing mechanism mounted in said frame structure and comprising a reciprocating yarn traverse guide element positioned adjacent said windup bobbin, said means comprising a movable linkage for controlling movement of the bobbin during growth of the yarn package thereon in a positive manner such that constant driving contact is maintained with the driven roll, the distance between the yarn traverse Iguide element and the surface of the yarn package remains less than a given limit, and the angle between the incoming yarn to the guide element and the yarn leaving the guide element remains less than a given desirable maximum limit, said mounting means comprising a swinging frame supported at one point by a first linkage of given efiective swinging radius and at a second point by a second linkage of swinging radius differing from said swinging radius of said first linkage so that the windup chuck and bobbin are positively restrained to move in a smoothly curved path during windup of the yarn.

2. The improved apparatus of claim '1 in which said swinging frame is provided with counterweight means and an opposed resilient means cooperating therewith to maintain a constant pressure between said yarn package and said drive roll during yarn windup.

3. The improved apparatus of claim 2 in which engaging means are provided on said swinging frame and said main supporting frame to cooperate for cushioning and limiting swinging frame movement in the apparatus.

References Cited in the file of this patent UNITED STATES PATENTS 2,752,100 Stange June 26, 1956 2,778,578 Keith Jan. 22, 1957 FOREIGN PATENTS 1,153,537 France Oct. 7, 1957 

